The Impact of Swelling Indices of Sokoto Clays on the Moulding Properties of the Clays in Sand Mixtures was investigated. Four clays (labeled A, B, C, D) from different locations in Sokoto state of Nigeria were sampled. The sampling method was that for each deposit five samples were taken at different positions and then mixed together. At the laboratory they were washed to remove organic matter and then dried at 110˚C in the oven. A laboratory ball mill was used to grind the dried clays. Each of the clay was then sampled for the determination of its swelling index. The determination of the moulding properties of the clays then followed. Only green compression strength, dry compression strength and green permeability, moulding properties were determined. The analysis of the result revealed that clay B has the highest green and dry strength values it had the highest green compression strength of 71.7 KN/m 2 and the highest dry compression strength of 3225.75 KN/m 2 . Clay B also has the highest swelling index of 60% and very high degree of expansiveness when compared to the other three clays. Clay B was followed by clay A with swelling index of 25%; the clay has high green and dry compression strength and a moderate degree of expansiveness. The inability of clay D with swelling index of 40% to be the next clay to clay B which has the highest swelling index of 60% among the four clays in terms of good moulding properties is an indication that high swelling index does not always mean good moulding properties in clay binders.